Aircraft early warning (AEW) surveillance radar systems use both electronic phased array and mechanically rotating antenna structures.
Although phased array radar systems have distinct advantages, aircraft mounted single antenna systems cannot generally search 360.degree. in azimuth. Nor can they reposition themselves quickly so as to cover critical sectors and skip sectors that are not of interest.
In the case of mechanically rotating antennas, large dome structures are customary and this produces drag--reducing aircraft performance. Reliability problems become apparent in rotating mechanical antenna structures due to the fact that RF power and analog signals must pass through a rotating joint. An additional problem is the customary fixed dwell time of sector surveillance thereby precluding increased dwell for critical sectors.